I agree wholeheartedly that the extended detachable magazines are fairly worthless even though many people think they "look cool". It is quicker to reload the SKS using the ten-round stripper clips as the after market detachable magazines are slow to position in the magazine well, greatly alter the balance of the rifle, and don't always feed correctly. I will, however, disagree that the SKS is "inherently inaccurate". First, because ALL military rifles of any country usually have to meet a specific criteria and a matter of accuracy with 4" groups at 100 yards being the maximum usually allowed. Second, ammunition used plays a major role in a rifle's accuracy.

I have three SKS rifles, each purchased between 1990 and 1992. They are a Chinese ex-military with stepped barrel, a Chinese commercial with pinned barrel, and a Russian ex-military. Each was new, unissued at the time of purchase. They are all extremely accurate by military and quite a few civilian standards. The worst group ever achieved with these rifles was 2" at 100 yards with the best being a half inch. I have used quite a variety of ammunition through each of these and others, both military surplus and commercially manufactured, American and foreign. The best I have found to date for accuracy and performance is Barnaul, made in Russia, followed closely by Silver Bear (made by Barnaul).

Scoping a SKS is very worthwhile as long as it is done properly. The receiver cover mounts where the scope sits directly on top of the cover, such as the B-Square, are worthless. The see-thru segments highly restrict one's field of view when using the open sights and the receiver mount is not solid enough for continued accuracy. The best method is to install a rail on the side of the receiver with the mount coming straight up using either off-cant rings (where scope is somewhat above and to the left of the receiver, in the manner of scoping a Winchester lever action rifle) or over-bore rings. My Chinese commercial was purchased in the "sniper configuration" with receiver rail, off-cant mount, 2.75 power scope, and a heavy bipod. This rifle can still hit a 2" object at 100 yards all day long without a problem. I know that William's Gun Sight Company used to have such a receiver rail and over-bore ring set but don't know if they still do. Also, if you wish to use a standard length scope a shell deflector will be necessary.  Williams also makes excellent replacements for the front and rear sights, both conventional and fiber optic, that fit in the original mountings.

The next best setup for scopes that does work is the Leaper's receiver cover mount. This mount has an over-bore design leaving a good field of view for using the open sights. The ring supports come up from the base at the left side of the cover and is very solid. The receiver cover also uses two set screws on each side for additional stabilization.

A shot out bore (worn) will always affect accuracy so you might consider having your rifle rebarreled.

As far as trajectory is concerned, I have had no problem being on target with any of my SKSes out to 300 yards, even with open sights. Yes, some cartridges in different calibers have a flatter trajectory than others but any bullet of any caliber or weight will start to drop once it has reached terminal velocity. That's why many military rifles have adjustable rear sights for elevation for longer range shooting. This is to compensate for bullet drop at distance.